Add support for package json

[alexewerlof]

I usually read package.json in typedoc.js to set the name parameter and append version to it.
It would be great if we could get CLI support for version and even better if typedoc could directly accept a param for package.json.

[Gozala]

Also a way to display what's the main module.

[Gerrit0]

#544 has been resolved, so the package version is now included by default.